Liquid nutritionally balanced food compositions are known in the art. See, for example, U.S. Pat. No. 4,931,300 to Monte for “ANTIMICROBIAL FOOD COMPOSITION.” Liquid nutritionally balanced powdered food compositions like those described in U.S. Pat. No. 4,931,300 have several potential disadvantages. Protein tends to precipitate from liquid solutions which, like the food composition in U.S. Pat. No. 4,931,300, have acidic pH values in the range of 2.0 to 5.5. In particular, protein tends to precipitate from such liquid solutions when the solutions are heated to a high temperature to commercially sterilize the solutions. However, solutions with low pH values in the range of 2.0 to 5.5 are often preferred for nutritional food compositions because the acidity of the solutions normally provides a high level of antimicrobial activity. Even so, the food composition in U.S. Pat. No. 4,931,300 must be refrigerated after it is reconstituted and must then be utilized within about seventy-two hours. Even though the seventy-two hour shelf life of the reconstituted food composition is relatively short, it is still substantially longer than the shelf life of other comparable food compositions. See, for example, U.S. Pat. No. 4,112,123 to Roberts, where the shelf life of a comparable reconstituted refrigerated food composition is only about twenty-four hours.
Some attempts to address these and other problems are illustrated in U.S. Pat. Nos. 5,156,875 and 5,614,241. Each of these patents utilize a water soluble protein, preferably whey protein, in conjunction with a protein stabilizer system to control precipitation of the proteins out of the aqueous food composition.
In practice, however, the food compositions of the type described in U.S. Pat. Nos. 4,931,300, 4,112,123, 5,156,875 and 5,614,241 have each encountered continued problems with precipitation of the proteins during storage in liquid form or after reconstitution with an aqueous medium such as water. The food compositions of U.S. Pat. Nos. 5,156,875 and 5,614,241 have both been found to undergo significant precipitation of the proteins after sterilization and packaging, thereby reducing the viable shelf life of the product.
Additionally, the prior food compositions of U.S. Pat. Nos. 4,931,300, 4,112,123, 5,156,875 and 5,614,241 all required aseptic sterilization and packaging. Aseptic sterilization, also called ultra high temperature/short time (UHTST) pasteurization, is generally a more restrictive and more expensive process than the general commercial retort sterilization used in typical canning processes for food products. Aseptic sterilization has a higher failure rate than commercial retort sterilization. Therefore, aseptic sterilization requires 100% inspection for swollen containers after an incubation period of 7-10 days before shipping. In Aseptic sterilization, the product and the packaging must each be separately sterilized prior to combining in an aseptic environment. By contrast, retort sterilization allows both the packaging and the food product within it to be sterilized simultaneously. However, the retort sterilization process requires more time at lower temperature levels to achieve levels of thermo-lethality comparable to aseptic sterilization. Retort sterilization was unsuitable for the prior art food compositions because such compositions broke down with subsequent protein precipitation during the longer periods during which the products were held at higher temperatures that characterize commercial retort sterilization processes.
Milk proteins have excellent nutritional and functional properties and are widely used in the manufacture of food products. Different functionality, composition and flavor of milk protein products make them ideal for a number of uses. Milk protein is a rich source of essential amino acids. Milk is made up of approximately 3-5 percent protein which can be classified into two basic types, casein proteins and whey proteins. About 80 percent of the protein content is casein which occurs as complexes or micelles in fresh milk, while the whey proteins are soluble in the milk's serum phase. Casein forms the largest part of the total protein content in cow's milk—around 80 percent—and so it is a valuable component.
All casein products are manufactured from skim milk using a similar basic process: the casein is separated from the milk, purified by washing, and dried. However, the process is a little different according to whether rennet or acid casein is being made.
Rennet casein is mainly used to make imitation cheese which has an important role in the fast food trade, although some is also used to manufacture plastic products such as buttons. Rennet casein is generally used in the manufacturing of products.
In its insoluble form, acid casein does not presently have many uses. To make it soluble, the casein is neutralized by adding an alkali. Alternatively, caseinates (which have different properties from casein) can be made by adding different dissolving salts to the insoluble acid casein. Both acid casein and caseinates, the salts of caseins, are widely used in the food industry and they have some technical uses also. Caseinates are made by dissolving acid casein in a suitable hydroxide and drying it to make a water soluble product.
Calcium caseinate is typically manufactured from fresh skim milk by precipitation of the casein through acidification. After separation, the fresh casein curd is washed, converted to calcium caseinate and dried. Calcium caseinate has a milky appearance and smooth mouth feel, making it ideal for use in powdered diet supplements, nutritional beverages and processed cheese.
Sodium caseinate is an extremely high quality milk protein fully reacted from edible acid casein. This top quality milk protein is heat stable with excellent emulsifying and binding capabilities which contribute to the stabilization of many food applications. Sodium caseinate is used extensively in the manufacture of coffee whiteners, whipped toppings, cream liqueurs, yogurt, processed cheese and meat products.
Calcium sodium caseinate is typically manufactured from fresh skim milk by precipitation of the casein through acidification. After separation, the fresh casein curd is washed, converted to calcium sodium caseinate and dried.
Potassium caseinate is a milk protein manufactured from fresh skim milk. Potassium caseinate can be used in a verity of food and pharmaceutical products, especially where low sodium levels are required.
Magnesium caseinate is a highly soluble magnesium source with excellent emulsifying and stabilizing properties for use in nutritional applications.
For the purposes of the present invention, caseinates are not necessarily dependant upon a process for production thereof.
Casein is the primary protein in milk protein concentrates and milk protein isolates, also known as total milk proteins (TMP's). Such milk protein concentrates and isolates contain all of the proteins found in milk and generally are about 80% casein and 20% whey proteins.
As seen in the discussion above, although casein forms approximately 80% of the total protein content in cow's milk, in an acidic environment, casein is insoluble. However, for nutritional food compositions, solutions with low pH values in the range of 2.0 to 5.5 are preferred because the acidity of the solutions normally provides a high level of antimicrobial activity. Thus it can be seen that because it has such high nutritional value, it would be desirable to convert casein into caseinates and utilize caseinates or milk protein concentrates and isolates containing mostly caseinates as the source of protein in antimicrobial food compositions.
Accordingly, it would be highly desirable to provide a process for producing liquid food compositions with low viscosity, pH in the range of about 2.0 to 5.5, high antimicrobial activity, extended shelf life at room temperature, utilizing caseinate as a protein source, and preventing protein from precipitating or settling from solution when the solution is sterilized using retort sterilization techniques.
Therefore, it is a principal object of the invention to provide an improved process for producing a food composition.
Another object of the invention is to provide a process utilizing caseinate in the manufacture of a low pH liquid food composition, which has a high antimicrobial activity and an extended shelf life.
Another object of the invention is to provide a low pH liquid food composition which is unusually stable at high temperatures and which includes caseinate as the primary protein source and which generally prevents protein from precipitating or separating from the liquid food composition.
A further object of the invention is to provide a nutritionally balanced liquid food composition, which includes a low pH protein stabilization system, has high antimicrobial activity and an extended shelf life at room temperature.
These and other, more specific objects and advantages of the invention will be apparent to those skilled in the art from the following detailed description thereof.